Microglia, the resident immune cells of the central nervous system, exhibit conserved developmental origins and core molecular signatures across vertebrate species, highlighting their crucial importance in the central nervous system. While homeostatic microglia maintain similar functions during phylogeny—such as immune surveillance, debris clearance, and synaptic pruning—their morphology, gene expression, and responses to stimuli remarkably vary by species. These differences reflect evolutionary divergence shaped by factors such as lifespan, regenerative potential, and immune architecture. This review integrates current findings from basic vertebrates such as zebrafish, rodents, and nonhuman primates with those from humans to highlight conserved and divergent aspects of microglial biology throughout evolution. Integrating these evolutionary differences is crucial for translating mechanistic insights across model organisms and advancing microglia-targeted therapies for neurological disorders.

Intracerebral hemorrhage (ICH) causes hematoma formation, leading to PHE, which is associated with leukocyte mobilization and increased inflammation at the site of brain injury. However, the fate of accumulated leukocytes within the hematoma and their impact on PHE expansion remain unknown. We performed single-cell immune profiling of hematoma cells from patients with acute ICH and reported a distinct phenotypic transformation of CD8+ T cells within the hematoma during the first 24 h after onset. In addition to enhanced IFN-γ production and migration capacity, these CD8+ T cells displayed remarkable glycolytic signatures. The metabolic fitness and functional reprogramming of hematomal CD8+ T cells are associated with the transcription factor FOXO1. Single-cell profiling of brain-infiltrating CD8+ T cells within the perihematomal tissues of ICH patients and cell culture assays revealed their capacity to activate microglia via the production of IFN-γ. Furthermore, the removal of hematomal CD8+ T cells reduced neuroinflammation, PHE expansion and neurological deficits in ICH mice. Thus, CD8+ T cells undergo metabolic and functional reprogramming within the hematoma during the acute phase of ICH, which contributes to PHE formation and neurological deterioration.Graphical FOXO1-driven metabolic reprogramming of hematomal CD8+ T cells drives the expansion of perihematomal edema following intracerebral hemorrhage—mechanisms and clinical implications CD8+ T cells within the hematoma are transformed during the first 24 h after ICH onset. These hematomal CD8+ T cells can possess remarkable glycolytic signatures and enhanced IFN-γ production and migration capacity, which are associated with the transcription factor FOXO1. The infiltration of CD8+ T cells in the brain augments perihematomal edema and neurological deterioration. (Figure created with BioRender).

Monkeypox, a zoonotic disease caused by the monkeypox virus (MPXV), has significant global public health implications. Inflammasomes serve as crucial components of the innate immune system, detecting pathogens and triggering cell death in infected cells to eliminate harmful agents. However, the precise molecular mechanisms governing the activation of inflammasomes during MPXV infection remain largely unclear. Using CRISPR-knockout cytosolic innate immune sensor screening, we identified AIM2 as the sensor for MPXV within the inflammasome, a trigger for inflammatory cell death. Mechanistically, AIM2 forms a complex with essential cell death molecules, including ASC and caspase-1 (CASP1), without interacting with RIPK3 or CASP8. Loss of ASC, CASP1, or gasdermin D (GSDMD) reduced cell death following MPXV infection, whereas loss of GSDME, CASP3, CASP6, CASP7, CASP9, RIPK3, or MLKL did not. Pyroptotic cell death was predominantly observed in infected cells, whereas apoptotic and necroptotic signaling pathways were primarily activated in uninfected bystander cells. Furthermore, we found that the transcription factor IRF1 serves as an upstream regulator of AIM2, controlling AIM2-dependent cell death. In experiments involving AIM2-deficient mice infected with MPXV, we observed a decrease in proinflammatory cytokines, multiple inflammatory cell death pathways, and leukocyte migration, culminating in increased viral spread. CAST/EiJ mice succumbed to high-dose MPXV infection within 8 days, whereas AIM2 inhibition increased survival, with 10% of the mice treated with an AIM2 inhibitor surviving the infection. In a low-dose infection model, AIM2 inhibition reduced IL-1β and IL-18 production, LDH release, and tissue pathology. These findings highlight the critical role of AIM2-mediated inflammasome activation, along with multiple programmed cell death pathways, in shaping the innate immune response to MPXV infection, offering valuable insights for developing therapeutic strategies targeting AIM2 and the broader innate immune response against monkeypox.

The microenvironment of distant organs affects the colonization and growth of disseminated tumor cells. It remains unclear how tumor-associated neutrophils are influenced by the microenvironment of distant organs. Here, we demonstrate that mature low-density neutrophils in colorectal cancer patients abnormally accumulate neutral lipids and induce the reactivation of dormant tumor cells, a process regulated by hepatic stellate cells. Mechanistically, activated hepatic stellate cells increased DGAT1/2-dependent lipid droplet synthesis in low-density neutrophils through the secretion of IL33, thereby maintaining the survival and immunosuppressive function of these neutrophils. The uptake of lipids from lipid-laden low-density neutrophils drives dormant tumor cell reactivation through the potentiation of β-oxidation and the stimulation of protumorigenic eicosanoid synthesis. In mouse models, targeting IL33 blocked neutrophil lipid synthesis, decreased the colonization of colorectal cancer cells in the liver, and enhanced the efficacy of immunotherapy. Overall, our study revealed that lipid accumulation in mature low-density neutrophils regulates the growth of dormant tumor cells and antitumor immunity to facilitate colorectal cancer liver metastasis. Targeting IL33 could be a promising therapeutic approach for colorectal cancer liver metastases.

Type 2high asthma, which accounts for the majority of asthma cases, is driven by Th2 cells that produce cytokines such as IL-4, IL-5, and IL-13. These cytokines promote several features of the disease, including eosinophilia, IgE production, bronchial hyperresponsiveness (BHR), mucus hypersecretion, and susceptibility to exacerbations. In contrast, type 2low asthma is characterized by the presence of neutrophils and reduced responsiveness to corticosteroids. In recent years, advances in our understanding of the distinct mechanisms at play in each asthma endotype have paved the way for the development of targeted therapies tailored to specific patient profiles. In this review, we first explore the underlying immunological mechanisms of various asthma endotypes. We also provide an overview of the different types of immunotherapies currently available to asthmatic patients and their clinical efficacy. Finally, we highlight emerging therapeutic strategies that hold promise for improving asthma management in the future.

Inflammasomes, particularly NLRC4, play crucial roles in immune responses to intracellular bacterial infections. However, gain-of-function mutations in NLRC4 are linked to severe autoinflammatory diseases, including autoinflammation with infantile enterocolitis (AIFEC). AIFEC patients who survive infancy typically have no further intestinal symptoms but retain susceptibility to macrophage activation syndrome (MAS). However, existing mouse models do not adequately replicate the inflammation observed in AIFEC patients. To better understand this, we developed a mouse model capable of conditional expression of the activating V341A mutation in NLRC4 (NLRC4-V341A KI). Global conversion to NLRC4-V341A at the germline resulted in symptoms closely mirroring those of human AIFEC, including severe infantile enterocolitis characterized by heightened intestinal inflammation, disrupted gut epithelium, compromised intestinal barrier integrity, severe diarrhea, and mortality within 10 days post-natally. Additionally, they displayed systemic autoinflammation marked by elevated levels of IL-1β, IL-18, and IL-6, alongside cytopenia and hemophagocytosis. In contrast, conditional conversion to NLRC4-V341A in adulthood caused systemic autoinflammation with only mild enterocolitis, mirroring AIFEC patients. Using this model, we demonstrated that IL-18 and TNF blockade effectively ameliorated AIFEC disease symptoms. Unexpectedly, glucose supplementation has emerged as a promising therapeutic strategy. These findings advance our understanding of AIFEC and illuminate the ways in which inflammasome activation contributes to very early onset inflammatory bowel disease (VEO-IBD) in the developing gut.

Interleukin-1 (IL-1) was the first interleukin identified as a potent proinflammatory and multifunctional molecule involved in innate immune responses against microbes, as well as in conditions of tissue injury associated with infections and sterile conditions. IL-1 is part of a large system, the IL-1 system, comprising a family of ligands that act as agonists, receptor antagonists, and anti-inflammatory cytokines, as well as a family of receptors that includes signaling receptor complexes, decoy receptors and negative regulators. All the members of the IL-1 system are involved in inflammatory diseases, innate and adaptive immune responses, conditions associated with dysmetabolism, and cancer by affecting both the tumor microenvironment and cancer cells. The deregulated or excessive activation of several pathways associated with the IL-1 system may lead to detrimental inflammatory or immune reactions, including autoinflammatory, autoimmune, infectious and degenerative diseases. The negative regulation of the IL-1 system mediated by antagonists, decoy receptors, scavengers, and dominant-negative molecules plays nonredundant roles in controlling these conditions. Owing to the central role of IL-1 in the pathogenesis of inflammation-driven diseases, IL-1 blocking agents are approved for clinical use in several inflammatory conditions, and inhibitory agents for other members of the family are under development. Here, the complexity of the IL-1 system, the involvement of its different members in inflammation-driven diseases, and the therapeutic approaches to target members of pathways associated with these conditions are presented and discussed.

The inflammasome is an inflammatory signaling protein complex comprising a sensor protein, the adaptor protein ASC, and the cysteine protease caspase-1. Inflammasome sensor proteins are activated by microbial molecular patterns, endogenous self-derived damage signals, or exogenous environmental danger signals. Multiple inflammasomes that differ in their mechanisms of action and structural composition have been identified. The best characterized are the canonical NLRP1, NLRP3, NAIP-NLRC4, AIM2, and Pyrin inflammasomes and the noncanonical inflammasomes activated by caspase-4, caspase-5 or caspase-11. The lesser known inflammasomes are the NLRP6, NLRP7, NLRP9, NLRP10, NLRP12, CARD8, and MxA inflammasomes. Following inflammasome assembly, caspase-1 promotes the secretion of the proinflammatory cytokines IL-1β and IL-18, and pyroptosis is mediated by the membrane-disrupting proteins gasdermin D and ninjurin-1. These functional activities control innate and adaptive immune responses and the initiation, development, and progression of autoinflammation, cancer, infectious diseases, and neurodegenerative diseases. Understanding how inflammasomes respond to pathogens and sterile signals has refined our view of innate immunity and offered new therapeutic targets. In this review, we present a comprehensive overview of inflammasomes with an emphasis on the mechanistic principles that govern inflammasome formation. We also discuss the contributions of inflammasome activation to health and disease.

Chronic inflammation can induce lymphocyte dysfunction, which is characterized by the expression of inhibitory immune checkpoints. For type 2 innate lymphoid cells (ILC2s), the acquisition of a state of hyporesponsiveness associated with PD-1 expression has been reported in severe allergic inflammation. However, the regulation of ILC2 reactivity in the context of cancer is less clear. The contribution of ILC2s to the antitumor immune response depends, indeed, on the type of tumor and the distinct cellular interplay within the microenvironment. Here, we show that ILC2s in malignant pleural effusions express the immune checkpoints PD-1 and CTLA-4. An in vitro model of the ILC2‒macrophage interaction demonstrated that this crosstalk is responsible for driving CTLA-4 expression and limiting ILC2 activation. Thus, by preventing ILC2 exhaustion, macrophages maintain ILC2 responsiveness to signals from the tissue. These results reveal that, unlike PD-1 expression, CTLA-4 expression on ILC2s is associated with the maintenance of a reactive state during chronic inflammation in the tumor microenvironment.